Talk to your health care provider to verify that sex is safe for you during your pregnancy. Intercourse and having an orgasm is usually safe.
Avoid sex if you are a placenta previa, an incompetent cervix, or preterm labor. You will often have uterine contractions if you have an orgasm, but it rarely will put you into labor.
It is best to avoid the traditional “missionary position” (man on top) after the fifth month due to pressure on the major blood vessels. Of course, avoid any position that causes discomfort.